Composite Manhole Cover with In-molded Components

ABSTRACT

A manhole cover is made of composite material with in-molded or encapsulated electronic and/or mechanical components. In some embodiments, the electronic components include a radio frequency identification device (RFID). In some embodiments, the electronic components includes sensors. In some embodiments, the electronic and/or mechanical components include switches, locks, and/or indicators.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. provisional application Ser. No. 62/432,941, filed Dec. 12, 2016.

FIELD

This invention relates to the field of underground utility access and more particularly to a composite manhole cover with molded-in electronic components.

BACKGROUND

Underground utility systems are used in cities across the world for infrastructure and maintenance. In order to do their job, municipal workers must enter the underground system in various locations across a city. Workers access these systems via manholes that are sealed with manhole covers. Manhole covers are often made of cast metals.

Many problems arise with the heavy, metal manhole covers. First, they are difficult and dangerous to lift and maneuver. Second, the manholes are a target for thieves that aim to salvage the metal for recycled scrap value. Third, gases produced in wastewater corrode the metal covers and frames weakening them or fusing them shut. Fourth, in some areas metal conducts extremely hot temperatures from steam transmission that burn pedestrians and their pets. Finally, a metal manhole cover can be lethal if a gas explosion launches the metal cover off of the manhole.

Another aspect of underground utility access systems is tracking, storing, and maintaining pertinent information about the systems. Useful information may include date of access, installation date, sewer depth, GPS location of manhole covers, manufacturing date, sewage flow rates, etc. A manhole cover including an electronic component allows municipal workers to track point-of-use information.

However, attaching the electronic component by fastening, fixturing, or mechanically adhering or chemically to the manhole cover degrades the properties of the composite. Fastening, fixturing, and mechanically adhering all require machining or abrading the composite surface after the part has completed the curing reaction. Boring and drilling holes into the molded part surface exposes the fiberglass and other subsurface ingredients. Penetrating the protective layer of chemical components at the molded surface reduces the composite's mechanical properties, chemical resistance, and long-term durability. Degradation is avoided by molding the electronic components inside the manhole cover. Molding the electronic components into metal manhole covers cannot be done because of the metal interferes with radio signals. But the composite manhole cover does not have that problem.

What is needed is a manhole cover that is lighter, durable, allows for molding in electronic components, and is less appealing to thieves. The solution is a manhole cover made of composite materials with in-molded or encapsulated electronic components.

SUMMARY

The disclosed invention encapsulates an electronic component or components into a manhole cover using composite molding processes so that municipal workers can identify, track, and maintain these assets.

Producing a manhole cover using the disclosed materials and processes allows for electronic and mechanical components to be molded within the manhole cover instead of externally attached to the manhole cover as was in the past. This reduces potential impact damage to the electronic component caused by snowplows, street sweepers, or other mechanical strikes; provides protection of the electronic components from chemical damage caused by sewer gases such as hydrogen sulfide; provides protection of the electronic components from weather elements such as ultraviolet light, rain, snow, and salt; and reduces incentives for theft. A lighter weight manhole cover reduces incidental damage caused by handling of the manhole cover or shocks caused by conduction with underground power lines. Further, such manhole covers enable radio frequency permeation and are more resilient to both high and low temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a top plan view of a composite manhole cover with in-molded electronic and/or mechanical component.

FIG. 2 illustrates a cross-sectional view of the composite manhole cover with in-molded electronic and/or mechanical component.

FIG. 3 illustrates an embodiment of the composite manhole cover with sensors.

FIG. 4 illustrates an embodiment of the composite manhole cover with a radio frequency identification (RFID) device.

DETAILED DESCRIPTION

Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures.

FIG. 1 shows a top plan view of a composite manhole cover 2 having molded within an electrical and/or mechanical component 4. FIG. 2 shows a side plan view of the composite manhole cover 2 having molded within an electrical and/or mechanical component 4. Note that the location of the electrical and/or mechanical device 4 is show as an example and it is fully anticipated that the electrical and/or mechanical device 4 be located at any location within the manhole cover 2, including on any surface of the manhole cover 2.

Although any use is anticipated for the electronic/mechanical components 4, one example is providing point-of-use information to municipal workers which will eliminate wasted time searching through archives and travelling away from the asset to administrative offices. Storing information will also reduce the frequency with which municipal workers need to open the manhole cover 2 to verify information about the underground utility system, thereby decreasing the chance of a workplace injury.

In some embodiments, identifying, tracking, and maintaining the assets and information is done with a central computer. In other embodiments, identifying, tracking, and maintaining the information is done with a handheld device.

As shown in FIG. 4, the in-molded electronic component 4 in some embodiments is a radio frequency identification (RFID) 10. RFIDs 10 are typically either active (powered by a power source 12 such as a battery) or passive (powered by the electromagnetic energy transmitted from an RFID reader). An RFID 10 sends information to reader device only after being prompted for that information by the reader device.

RFIDs include a factory programmed identification value that uniquely identifies each particular RFID 10.

In some embodiments, the RFID 10 is coated with a polymer insulator 14 that protects the RFID 10 and other components from abrasion, high pressure, and high temperatures that are present during the composite molding process. The polymer insulator 14 coats the electronic components 4 before insertion into the composite manhole cover 2. Examples of materials used for the polymer insulator 14 include, but are not limited to, unsaturated polyester, vinyl ester, epoxy, or a blend of these, with a compatible monomer to dissolve the polymer in solution. Compatible monomers include, but are not limited to, styrene, vinyl toluene, diallyl phthalate, and bisphenol A.

In some embodiments, an electronic or electro-mechanical system is molded within the manhole cover 2.

FIG. 3 shows one exemplary electro-mechanical system molded within a manhole cover 2. In this example, a processor 30 (e.g., programmable interrupt controller—PIC, controller, any processing element, discrete components for controlling) receives inputs from one or more sensors 34/38. Examples of such sensors 34/38 include, but are not limited to, gas sensors, light sensors, fluid depth sensors, moisture sensors, tamper sensors 38, etc. The processor 30 receives input data from the sensors 34/38. The data is processed and/or stored within a memory of the processor 30. Eventually, the data (or processed data) is emitted outside of the manhole cover 2, in this example, through a transmitter 32. The transmitter 32 sends the data to an external receiver over radio waves or light waves. In some embodiments, due to power restrictions and therefore limited range, the external receiver must be near the manhole cover 2 while on other embodiments, the receiver is centrally located for communications with many manhole covers 2. In some embodiments, the transmitter 32 further includes receiving capabilities for reasons including configuration management, control, and acknowledgement.

Power is provide to the processor 30, sensors 34/38, and transmitter 32 by a power subsystem 36 that includes a device for power storage (e.g., a battery, super capacitor) and, in some embodiments, includes a solar collector 40 that is used to recharge the device for power storage.

For example, back flow of sewage in sanitary system is detected and an alarm is signaled by a fluid depth sensor 34 in the manhole cover 2 before the fluid level reaches the street. Another example includes detecting when a manhole cover 2 is opened by a micro-switch sensor 38 so that steps can be taken to understand why one has accessed the manhole without authorization. Another example is using a sensor 34 to measure a gas concentration level inside the sewer, perhaps preventing accidental death from fatal exposures to hydrogen sulfide gas.

Now turning to a discussion of composite molding processes generally.

Methods of making a composite manhole cover 2 include glass fiber reinforced plastic (GFRP) techniques like polymer concrete, cast polymer, resin transfer molding, resin infusion, filament winding, gun chopped fiberglass and resin that is applied directly by an applicator, a brush, roller, hand spreader, or sprayer—often referred to as spray-up layup.

Newer, high volume methods called sheet molding compounds (SMC), thick molding compounds (TMC), and bulk molding compounds (BMC) have been used to mold composites in less time than GFRP methods.

The composite manhole cover 2 is made of a fiber reinforced thermosetting resin compound. Examples of thermosetting resin compounds include: polyester resin, polyurethanes, phenol-formaldehyde resins, urea-formaldehyde, benzoxazines, epoxy resin, diallyl-phthalate, polyimides, furan, silicone, and vinyl ester. Before the compound has set and formed the composite manhole cover 2, a composite mixture is prepared. The composite mixture is made with three major components: resins, fibers, and fillers. The three major ingredients account for ninety to ninety-five percent of the composite by weight. The remaining five to ten percent includes mold release agents, chemical initiators, pigments, thickeners, shrink control additives, and inhibitors.

Resins are supplied in a liquid form so that the fibers, fillers, and other additives blend in a homogeneous way. Resins are made with unsaturated polyesters, vinyl esters, epoxies, and blends of these.

In embodiments using glass fiber reinforcements, glass fibers are made from a low-alkali borosilicate glass formulation known as “E glass.” E glass is melted and blended then cooled and solidified. The solid glass forms strands of fiber that are collected in spools. These spools are used to form various weaves, chopped strands, mats, rovings, ropes, or other presentations. All presentations of the glass fiber give the composite manhole cover 2 stronger mechanical properties and are selected based on geometry and end-use application.

Fillers are added to the composite mixture to reduce cost, increase the viscosity, and give the composite manhole cover 2 properties such as flame retardance, corrosion resistance, increased density, low shrinkage, hardness, and electrical properties. Fillers are inorganic minerals. Suitable fillers include calcium carbonate, aluminum trihydrate, clay, calcium sulfate, barium sulfate, and silicates. These fillers are formed by milling, grinding, and/or precipitating the minerals into particles and separating the particles into a range of sizes. Suitable filler particle sizes range from one micron to one hundred microns.

Mold release agents are added to the composite mixture to ensure that the composite manhole cover 2 does not stick to the mold surface after curing. In some embodiments, the mold release agents are fatty acids. Exemplary fatty acids include calcium stearates, zinc stearates, and magnesium stearates. In other embodiments, alkyl phosphates are used.

Initiators are added to the composite mixture to start the chemical reaction resulting in cross-linking of the resins. In some embodiments, initiators are organic peroxides like diacyl peroxides, peroxy esters, diperoxy ketals, dialkyl peroxides. Some organic peroxides are activated with heat and pressure while some organic peroxides are activated with photo initiators.

Optionally, it is desirable to change the color or provide ultraviolet resistance for the composite manhole cover 2. In some embodiments, pigments are added to the composite mixture to create colors and impart ultraviolet resistance. An exemplary pigment is carbon black.

Thickeners are used to increase the viscosity of the composite mixture. Exemplary thickeners are calcium oxide, calcium hydroxide, magnesium oxide, magnesium hydroxide, fused silica, and water.

In some embodiments, shrink control additives are included in the composite mixture. Shrink control additives reduce the contraction of the composite mixture during the curing process. This is accomplished with thermoplastic additives like polyethylene, polystyrene, polyvinyl chloride, cellulose acetate and butyrate, polycaprolactone, polyvinyl acetate, polymethyl methacrylate, and thermoplastic polyesters.

In some embodiments, inhibitors are included to prevent premature curing. Suitable inhibitors include hydroquinone, parabenzoquinone, tertiary butyl catechol, tertiary butyl hydroquinone, and 2,6-ditertiary butyl-4-methyl phenol.

Now turning to a discussion of preparing the composite mixture for production of the manhole cover 2.

First, the liquid and small volume additive constituents (e.g. resins, initiators, inhibitors, pigments, shrink control agents) are blended in a high shear, high speed dispersions to create a homogenous liquid slurry.

Next, in embodiments using the BMC method, the liquid slurry is blended with the fibers and fillers in a low shear mixer. In embodiments using the SMC or TMC method, the liquid slurry is added directly to the other ingredients and blended with rollers that squeeze the materials together.

The composite mixture is inserted into the mold manually, robotically, by a gravity system, by a vacuum pull, by a pump, or with a pneumatic sprayer.

In some embodiments, a higher strength rating is required (e.g. airport runways). In these embodiments, an extra reinforcement of fiber glass roving, pultrusion, glass prepregs, or other higher strength support may be placed in the cavity of the mold before adding the composite mixture.

Next, the electronic components 4 are added to the composite mixture.

After the composite mixture and any electronic or mechanical components 4 are in the mold, curing is initiated. Depending on the embodiment, the electronic or mechanical components that are added to the mold optionally include RFID 10, power source 12, processor 30, transmitter 32, sensors 34/38, power subsystem 36, and solar collector 40.

In some embodiments, the composite mixture is cured under high temperature and pressure (approximately 270 to 350 degrees Fahrenheit and 500 to 1500 pounds per square inch). In other embodiments, the composite mixture is cured at ambient temperature and pressure.

After curing is complete, the composite manhole cover 2 is extracted from the mold cavity. The end product is a composite manhole cover 2, optionally including electronic components and/or mechanical components.

The electronic components (e.g. transmitter 32, RFID 10) communicate with an external device. In some embodiments, this communication includes information such as serial number, GPS location, manufacturing date, installation date, inspection date, sewer depth, flow direction, connections, inlets, drop pipes, lift stations, offsets, riser rings, cone type, manhole wall material, installer, inspector, processing station identification, maintenance date, photographs, and other pertinent information to the municipality or owner.

Although some RFIDs 10 have user memory, it is anticipated that in some embodiments, most of the data will be transferred and stored on an external device and/or downloaded to a remote computer. Some examples of data stored in the user memory will be predetermined while some types of data will be determined by the municipality or owner of the manhole cover 2. In addition to static identification data, the system will allow entry of variable data inputs, such as current condition of the manhole and manhole cover 2, sewer effluent levels and other observations and measurements recorded during a scheduled preventive maintenance review, programmed register, or corrective/containment action.

Municipalities also invest in Capital Asset Tracking (CAT) and/or geographic information system or (GIS) software that maps the location and topography of the municipal assets throughout the city. Information gathered by the electronic component 4 is uploaded onto current CAT/GIS software platforms (eg. Arc Gis, Cityworks, Cartograf) in a “.xml” file format so that cities can have up to date condition and status reports on these specific assets stored on their current computer system.

Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result.

It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description.

It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes. 

What is claimed is:
 1. A manhole cover, the manhole cover comprising: a body made of a composite polymer; a radio frequency identification tag coated with an insulating polymer; and the radio frequency identification tag embedded within the body; wherein the radio frequency identification tag is in communication with at least one sensor and a transmitter; whereby the at least one sensor collects data from a surrounding environment of the manhole cover and the transmitter transmits the data to a handheld reader.
 2. The manhole cover of claim 1, wherein the composite polymer is a thermosetting resin or a mixture of thermosetting resins
 3. The manhole cover of claim 1, wherein the at least one sensor senses and stores data including: temperature, duration of open state of manhole cover, duration of closed state of manhole cover, whether hydrogen sulfide gas is present, and depth of fluid beneath manhole cover.
 4. The manhole cover of claim 1, wherein the insulating polymer is selected from the group consisting of: unsaturated polyester, vinyl ester, and epoxy.
 5. The manhole cover of claim 1, wherein the composite polymer includes pigments to provide ultraviolet resistance.
 6. The manhole cover of claim 1, wherein the body further comprises fiberglass blended with the composite polymer.
 7. The manhole cover of claim 1, further comprising a power source to power the radio frequency identification tag and the at least one sensor.
 8. A manhole cover with in-molded electronic components, the manhole cover comprising: a body, the body formed of a thermosetting polymer; a radio frequency identification (RFID) tag; the RFID tag having an insulating coating; and the RFID tag mixed into the thermosetting polymer prior to curing.
 8. The manhole cover of claim 8, wherein the insulating coating is selected from the group consisting of: unsaturated polyester, vinyl ester, and epoxy.
 9. The manhole cover of claim 8, further comprising at least one sensor; the at least one sensor in communication with the RFID tag; the at least one sensor located external to the manhole cover; and wherein the at least one sensor senses and stores data including: temperature, duration of open state of manhole cover, duration of closed state of manhole cover, whether hydrogen sulfide gas is present, and depth of fluid beneath manhole cover.
 10. The manhole cover of claim 8, further comprising a pigment mixed into the thermosetting polymer, whereby the pigment provides ultraviolet resistance.
 11. The manhole cover of claim 8, further comprising a power source embedded within the body of the manhole cover, the power source for powering the at least one sensor.
 12. The manhole cover of claim 8, wherein the thermosetting polymer is reinforced with fiberglass.
 13. The manhole cover of claim 8, wherein the thermosetting polymer is a mixture of one or more of the following: polyester resin, polyurethanes, phenol-formaldehyde resins, urea-formaldehyde, benzoxazines, epoxy resin, diallyl-phthalate, polyimides, furan, silicone, and vinyl ester.
 14. A composite polymer manhole cover with embedded electronic components, the composite polymer manhole cover comprising: a body; a radio frequency identification (RFID) tag; at least one sensor; at least one transmitter; the RFID tag coated with an insulating polymer; and the RFID tag embedded within the body of the composite polymer manhole cover.
 15. The composite polymer manhole cover of claim 14, wherein the body is formed by molding a mixture of a thermosetting resin, a fiber, and one or more filler compounds.
 16. The composite polymer manhole cover of claim 15, wherein the mixture is made from a thermosetting resin selected from the group consisting of: polyester resin, polyurethanes, phenol-formaldehyde resins, urea-formaldehyde, benzoxazines, epoxy resin, diallyl-phthalate, polyimides, furan, silicone, and vinyl ester.
 17. The composite polymer manhole cover of claim 14, wherein: the insulating polymer is a mixture of a polymer and a compatible monomer; the polymer is selected from the group consisting of: unsaturated polyester, vinyl ester, and epoxy; the compatible monomer is selected from the group consisting of: styrene, vinyl toluene, daillyl phthalate, and bisphenol A; and whereby the compatible monomer aids in dissolving the polymer in solution.
 18. The composite polymer manhole cover of claim 14, further comprising a power source coated and embedded within the composite polymer manhole cover.
 19. The composite polymer manhole cover of claim 14, wherein: the at least one sensor is located external to the composite polymer manhole cover; and the at least one sensor is in communication with the RFID tag; whereby information is transmitted at regular intervals to a central computer database. 